Actuator with deadbeat control

ABSTRACT

An electromagnetic actuation system includes an actuator having an electrical coil, a magnetic core, and an armature. The system further includes a controllable bi-directional drive circuit for selectively driving current through the electrical coil in either of two directions. The control module provides an actuator command to the drive circuit effective to drive current through the electrical coil in a first direction to actuate the armature and in a second direction subsequent to armature actuation to oppose residual flux within the actuator. The control module includes a residual flux feedback control module configured to adapt the actuator command to converge residual flux within the actuator to a preferred flux level.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/968,026, filed on Mar. 20, 2014, U.S. Provisional Application No.61/968,039, filed on Mar. 20, 2014, and U.S. Provisional Application No.61/955,942, filed on Mar. 20, 2014, all of which are incorporated hereinby reference.

TECHNICAL FIELD

This disclosure is related to solenoid-activated actuators.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure. Accordingly, such statements are notintended to constitute an admission of prior art.

Solenoid actuators can be used to control fluids (liquids and gases), orfor positioning or for control functions. A typical example of asolenoid actuator is the fuel injector. Fuel injectors are used toinject pressurized fuel into a manifold, an intake port, or directlyinto a combustion chamber of internal combustion engines. Known fuelinjectors include electromagnetically-activated solenoid devices thatovercome mechanical springs to open a valve located at a tip of theinjector to permit fuel flow therethrough. Injector driver circuitscontrol flow of electric current to the electromagnetically-activatedsolenoid devices to open and close the injectors. Injector drivercircuits may operate in a peak-and-hold control configuration or asaturated switch configuration.

Fuel injectors are calibrated, with a calibration including an injectoractivation signal including an injector open-time, or injectionduration, and a corresponding metered or delivered injected fuel massoperating at a predetermined or known fuel pressure. Injector operationmay be characterized in terms of injected fuel mass per fuel injectionevent in relation to injection duration. Injector characterizationincludes metered fuel flow over a range between high flow rateassociated with high-speed, high-load engine operation and low flow rateassociated with engine idle conditions.

It is known for engine control to benefit from injecting a plurality ofsmall injected fuel masses in rapid succession. Generally, when a dwelltime between consecutive injection events is less than a dwell timethreshold, injected fuel masses of subsequent fuel injection eventsoften result in a larger delivered magnitude than what is desired eventhrough equal injection durations are utilized. Accordingly, suchsubsequent fuel injection events can become unstable resulting inunacceptable repeatability. This undesirable occurrence is attributed tothe existence of residual magnetic flux within the fuel injector that isproduced by the preceding fuel injection event that offers someassistance to the immediately subsequent fuel injection event. Theresidual magnetic flux is produced in response to persistent eddycurrents and magnetic hysteresis within the fuel injector as a result ofshifting injected fuel mass rates that require different initialmagnetic flux values.

SUMMARY

An electromagnetic actuation system includes an actuator having anelectrical coil, a magnetic core, and an armature. The system furtherincludes a controllable bi-directional drive circuit for selectivelydriving current through the electrical coil in either of two directions.The control module provides an actuator command to the drive circuiteffective to drive current through the electrical coil in a firstdirection to actuate the armature and in a second direction subsequentto armature actuation to oppose residual flux within the actuator. Thecontrol module includes a residual flux feedback control moduleconfigured to adapt the actuator command to converge residual fluxwithin the actuator to a preferred flux level.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1-1 illustrates a schematic sectional view of a fuel injector andan activation controller, in accordance with the present disclosure;

FIG. 1-2 illustrates a schematic sectional view of the activationcontroller of FIG. 1-1, in accordance of the present disclosure;

FIG. 1-3 illustrates a schematic sectional view of an injector driver ofFIGS. 1-1 and 1-2, in accordance to the present disclosure;

FIG. 2 illustrates a non-limiting exemplary first plot 1000 of measuredcurrent and fuel flow rate and a non-limiting exemplary second plot 1010of measured main excitation coil and search coil voltages for twosuccessive fuel injection events having identical current pulses thatare separated by a dwell time that is not indicative of being closelyspaced, in accordance with the present disclosure;

FIG. 3 illustrates a non-limiting exemplary first plot 1020 of measuredcurrent and fuel flow rate and a non-limiting exemplary second plot 1030of measured main excitation coil and search coil voltages for twosuccessive fuel injection events having identical current pulses thatare separated by a dwell time that is indicative of being closelyspaced, in accordance with the present disclosure;

FIG. 4 illustrates a series of non-limiting exemplary plots 1300, 1310and 1320, representing measured coil current, magnetic force andmagnetic flux in a fuel injector, wherein current provided to the coilis being controlled in a unidirectional manner, in accordance with thepresent disclosure;

FIG. 5 illustrates a non-limiting exemplary plot of measured current andflow rate for two successive fuel injection events having identicalbi-directionally applied current pulses that are separated by a dwelltime that is indicative of being closely spaced, in accordance with thepresent disclosure;

FIG. 6 illustrates a non-limiting exemplary plot 1500 for measuredcurrent and measured magnetic and a non-limiting exemplary plot 1502 formeasured search coil voltage for two successive fuel injection eventshaving identical current pulses separated by a dwell time, in accordancewith the present disclosure;

FIG. 7 illustrates an exemplary embodiment of a deadbeat flux controlmodule using search coil voltage feedback to control an optimum durationat which a negative current is applied to an electromagnetic coil of afuel injector to reduce residual flux therein, in accordance with thepresent disclosure;

FIG. 8 illustrates a series of non-limiting exemplary plots 1330, 1340and 1350, representing measured coil current, magnetic force andmagnetic flux in a fuel injector, wherein flux is controlled usingcurrent applied to the fuel injector in a bi-directional manner, inaccordance with the present disclosure.

DETAILED DESCRIPTION

This disclosure describes the concepts of the presently claimed subjectmatter with respect to an exemplary application to linear motion fuelinjectors. However, the claimed subject matter is more broadlyapplicable to any linear or non-linear electromagnetic actuator thatemploys an electrical coil for inducing a magnetic field within amagnetic core resulting in an attractive force acting upon a movablearmature. Typical examples include fluid control solenoids, gasoline ordiesel or CNG fuel injectors employed on internal combustion engines andnon-fluid solenoid actuators for positioning and control.

Referring now to the drawings, wherein the showings are for the purposeof illustrating certain exemplary embodiments only and not for thepurpose of limiting the same, FIG. 1-1 schematically illustrates anon-limiting exemplary embodiment of an electromagnetically-activateddirect-injection fuel injector 10. While anelectromagnetically-activated direct-injection fuel injector is depictedin the illustrated embodiment, a port-injection fuel injector is equallyapplicable. The fuel injector 10 is configured to inject fuel directlyinto a combustion chamber 100 of an internal combustion engine. Anactivation controller 80 electrically operatively connects to the fuelinjector 10 to control activation thereof. The activation controller 80corresponds to only the fuel injector 10. In the illustrated embodiment,the activation controller 80 includes a control module 60 and aninjector driver 50. The control module 60 electrically operativelyconnects to the injector driver 50 that electrically operativelyconnects to the fuel injector 10 to control activation thereof. Feedbacksignal(s) 42 may be provided from the fuel injector to the actuationcontroller 80.The fuel injector 10, control module 60 and injectordriver 50 may be any suitable devices that are configured to operate asdescribed herein. In the illustrated embodiment, the control module 60includes a processing device. In one embodiment, one or more componentsof the activation controller 80 are integrated within a connectionassembly 36 of the fuel injector 36. In another embodiment, one or morecomponents of the activation controller 80 are integrated within a body12 of the fuel injector 10. In even yet another embodiment, one or morecomponents of the activation controller 80 are external to—and in closeproximity with—the fuel injector 10 and electrically operativelyconnected to the connection assembly 36 via one or more cables and/orwires. The terms “cable” and “wire” will be used interchangeably hereinto provide transmission of electrical power and/or transmission ofelectrical signals.

Control module, module, control, controller, control unit, processor andsimilar terms mean any one or various combinations of one or more ofApplication Specific Integrated Circuit(s) (ASIC), electroniccircuit(s), central processing unit(s) (preferably microprocessor(s))and associated memory and storage (read only, programmable read only,random access, hard drive, etc.) executing one or more software orfirmware programs or routines, combinational logic circuit(s),input/output circuit(s) and devices, appropriate signal conditioning andbuffer circuitry, and other components to provide the describedfunctionality. Software, firmware, programs, instructions, routines,code, algorithms and similar terms mean any instruction sets includingcalibrations and look-up tables. The control module has a set of controlroutines executed to provide the desired functions. Routines areexecuted, such as by a central processing unit, and are operable tomonitor inputs from sensing devices and other networked control modules,and execute control and diagnostic routines to control operation ofactuators. Routines may be executed at regular intervals, for exampleeach 3.125, 6.25, 12.5, 25 and 100 milliseconds during ongoing engineand vehicle operation. Alternatively, routines may be executed inresponse to occurrence of an event.

In general, an armature is controllable to one of an actuated positionand a static or rest position. The fuel injector 10 may be any suitablediscrete fuel injection device that is controllable to one of an open(actuated) position and a closed (static or rest) position. In oneembodiment, the fuel injector 10 includes a cylindrically-shaped hollowbody 12 defining a longitudinal axis 101. A fuel inlet 15 is located ata first end 14 of the body 12 and a fuel nozzle 28 is located at asecond end 16 of the body 12. The fuel inlet 15 is fluidly coupled to ahigh-pressure fuel line 30 that fluidly couples to a high-pressureinjection pump. A valve assembly 18 is contained in the body 12, andincludes a needle valve 20, a spring-activated pintle 22 and an armatureportion 21. The needle valve 20 interferingly seats in the fuel nozzle28 to control fuel flow therethrough. While the illustrated embodimentdepicts a triangularly-shaped needle valve 20, other embodiments mayutilize a ball. In one embodiment, the armature portion 21 is fixedlycoupled to the pintle 22 and configured to linear translate as a unitwith the pintle 22 and the needle valve 20 in first and seconddirections 81, 82, respectively. In another embodiment, the armatureportion 21 may be slidably coupled to the pintle 22. For instance, thearmature portion 21 may slide in the first direction 81 until beingstopped by a pintle stop fixedly attached to the pintle 22. Likewise,the armature portion 21 may slide in the second direction 82 independentof the pintle 22 until contacting a pintle stop fixedly attached to thepintle 22. Upon contact with the pintle stop fixedly attached to thepintle 22, the force of the armature portion 21 causes the pintle 22 tobe urged in the second direction 82 with the armature portion 21. Thearmature portion 21 may include protuberances to engage with variousstops within the fuel injector 10.

An annular electromagnet assembly 24, including an electrical coil andmagnetic core, is configured to magnetically engage the armature portion21 of the valve assembly. The electrical coil and magnetic core assembly24 is depicted for illustration purposes to be outside of the body ofthe fuel injector; however, embodiments herein are directed toward theelectrical coil and magnetic core assembly 24 to be either integral to,or integrated within, the fuel injector 10. The electrical coil is woundonto the magnetic core, and includes terminals for receiving electricalcurrent from the injector driver 50. Hereinafter, the “electrical coiland magnetic core assembly” will simply be referred to as an “electricalcoil 24”. When the electrical coil 24 is deactivated and de-energized,the spring 26 urges the valve assembly 18 including the needle valve 20toward the fuel nozzle 28 in the first direction 81 to close the needlevalve 20 and prevent fuel flow therethrough. When the electrical coil 24is activated and energized, electromagnetic force (herein after“magnetic force”) acts on the armature portion 21 to overcome the springforce exerted by the spring 26 and urges the valve assembly 18 in thesecond direction 82, moving the needle valve 20 away from the fuelnozzle 28 and permitting flow of pressurized fuel within the valveassembly 18 to flow through the fuel nozzle 28. A search coil 25 ismutually magnetically coupled to the electrical coil 24 and ispreferably wound axially or radially adjacent coil 24. Search coil 25 isutilized as a sensing coil as described in further detail below.

The fuel injector 10 may include a stopper 29 that interacts with thevalve assembly 18 to stop translation of the valve assembly 18 when itis urged to open. In one embodiment, a pressure sensor 32 is configuredto obtain fuel pressure 34 in the high-pressure fuel line 30 proximal tothe fuel injector 10, preferably upstream of the fuel injector 10. Inanother embodiment, a pressure sensor may be integrated within the inlet15 of the fuel injector in lieu of the pressure sensor 32 in the fuelrail 30 or in combination with the pressure sensor. The fuel injector 10in the illustrated embodiment of FIG. 1-1 is not limited to the spatialand geometric arrangement of the features described herein, and mayinclude additional features and/or other spatial and geometricarrangements known in the art for operating the fuel injector 10 betweenopen and closed positions for controlling the delivery of fuel to theengine 100.

The control module 60 generates an injector command (actuator command)signal 52 that controls the injector driver 50, which activates the fuelinjector 10 to the open position for affecting a fuel injection event.In the illustrated embodiment, the control module 60 communicates withone or more external control modules such as an engine control module(ECM) 5; however, the control module 60 may be integral to the ECM inother embodiments. The injector command signal 52 correlates to adesired mass of fuel to be delivered by the fuel injector 10 during thefuel injection event. Similarly, the injector command signal 52 maycorrelate to a desired fuel flow rate to be delivered by the fuelinjector 10 during the fuel injection event. As used herein, the term“desired injected fuel mass” refers to the desired mass of fuel to bedelivered to the engine by the fuel injector 10. As used herein, theterm “desired fuel flow rate” refers to the rate at which fuel is to bedelivered to the engine by the fuel injector 10 for achieving thedesired mass of fuel. The desired injected fuel mass can be based uponone or more monitored input parameters 51 input to the control module 60or ECM 5. The one or more monitored input parameters 51 may include, butare not limited to, an operator torque request, manifold absolutepressure (MAP), engine speed, engine temperature, fuel temperature, andambient temperature obtained by known methods. The injector driver 50generates an injector activation (actuator activation) signal 75 inresponse to the injector command signal 52 to activate the fuel injector10. The injector activation signal 75 controls current flow to theelectrical coil 24 to generate electromagnetic force in response to theinjector command signal 52. An electric power source 40 provides asource of DC electric power for the injector driver 50. In someembodiments, the DC electric power source provides low voltage, e.g., 12V, and a boost converter may be utilized to output a high voltage, e.g.,24V to 200 V, that is supplied to the injector driver 50. When activatedusing the injector activation signal 75, the electromagnetic forcegenerated by the electrical coil 24 urges the armature portion 21 in thesecond direction 82. When the armature portion 21 is urged in the seconddirection 82, the valve assembly 18 in consequently caused to urge ortranslate in the second direction 82 to an open position, allowingpressurized fuel to flow therethrough. The injector driver 50 controlsthe injector activation signal 75 to the electrical coil 24 by anysuitable method, including, e.g., pulsewidth-modulate (PWM) electricpower flow. The injector driver 50 is configured to control activationof the fuel injector 10 by generating suitable injector activationsignals 75. In embodiments that employ a plurality of successive fuelinjection events for a given engine cycle, an injector activation signal75 that is fixed for each of the fuel injection events within the enginecycle may be generated.

The injector activation signal 75 is characterized by an injectionduration and a current waveform that includes an initial peak pull-incurrent and a secondary hold current. The initial peak pull-in currentis characterized by a steady-state ramp up to achieve a peak current,which may be selected as described herein. The initial peak pull-incurrent generates electromagnetic force that acts on the armatureportion 21 of the valve assembly 18 to overcome the spring force andurge the valve assembly 18 in the second direction 82 to the openposition, initiating flow of pressurized fuel through the fuel nozzle28. When the initial peak pull-in current is achieved, the injectordriver 50 reduces the current in the electrical coil 24 to the secondaryhold current. The secondary hold current is characterized by a somewhatsteady-state current that is less than the initial peak pull-in current.The secondary hold current is a current level controlled by the injectordriver 50 to maintain the valve assembly 18 in the open position tocontinue the flow of pressurized fuel through the fuel nozzle 28. Thesecondary hold current is preferably indicated by a minimum currentlevel. The injector driver 50 is configured as a bi-directional currentdriver capable of providing a negative current flow for drawing currentfrom the electrical coil 24. As used herein, the term “negative currentflow” refers to the direction of the current flow for energizing theelectrical coil to be reversed. Accordingly, the terms “negative currentflow” and “reverse current flow” are used interchangeably herein.

Embodiments herein are directed toward controlling the fuel injector fora plurality of fuel injection events that are closely-spaced during anengine cycle. As used herein, the term “closely-spaced” refers to adwell time between each consecutive fuel injection event being less thana predetermined dwell time threshold. As used herein, the term “dwelltime” refers to a period of time between an end of injection for thefirst fuel injection event (actuator event) and a start of injection fora corresponding second fuel injection event (actuator event) of eachconsecutive pair of fuel injection events. The dwell time threshold canbe selected to define a period of time such that dwell times less thanthe dwell time threshold are indicative of producing instability and/ordeviations in the magnitude of injected fuel mass delivered for each ofthe fuel injection events. The instability and/or deviations in themagnitude of injected fuel mass may be responsive to a presence ofsecondary magnetic effects. The secondary magnetic effects includepersistent eddy currents and magnetic hysteresis within the fuelinjector and a residual flux based thereon. The persistent eddy currentsand magnetic hysteresis are present due to transitions in initial fluxvalues between the closely-spaced fuel injection events. Accordingly,the dwell time threshold is not defined by any fixed value, andselection thereof may be based upon, but not limited to, fueltemperature, fuel injector temperature, fuel injector type, fuelpressure and fuel properties such as fuel types and fuel blends. As usedherein, the term “flux” refers to magnetic flux indicating the totalmagnetic field generated by the electrical coil 24 and passing throughthe armature portion. Since the turns of the electrical coil 24 link themagnetic flux in the magnetic core, this flux can therefore be equatedfrom the flux linkage. The flux linkage is based upon the flux densitypassing through the armature portion, the surface area of the armatureportion adjacent to the air gap and the number of turns of the coil 24.Accordingly, the terms “flux”, “magnetic flux” and “flux linkage” willbe used interchangeably herein unless otherwise stated.

For fuel injection events that are not closely spaced, a fixed currentwaveform independent of dwell time may be utilized for each fuelinjection event because the first fuel injection event of a consecutivepair has little influence on the delivered injected fuel mass of thesecond fuel injection event of the consecutive pair. However, the firstfuel injection event may be prone to influence the delivered injectedfuel mass of the second fuel injection event, and/or further subsequentfuel injection events, when the first and second fuel injection eventsare closely-spaced and a fixed current wave form is utilized. Any time afuel injection event is influenced by one or more preceding fuelinjection events of an engine cycle, the respective delivered injectedfuel mass of the corresponding fuel injection event can result in anunacceptable repeatability over the course of a plurality of enginecycles and the consecutive fuel injection events are consideredclosely-spaced. More generally, any consecutive actuator events whereinresidual flux from the preceding actuator event affects performance ofthe subsequent actuator event relative to a standard, for examplerelative to performance in the absence of residual flux, are consideredclosely-spaced

FIG. 1-2 illustrates the activation controller 80 of FIG. 1-1, inaccordance with the present disclosure. Signal flow path 362 providescommunication between the control module 60 and the injector driver 50.For instance, signal flow path 362 provides the injector command signal(e.g., command signal 52 of FIG. 1-1) that controls the injector driver50. The control module 60 further communicates with the external ECM 5via signal flow path 364 within the activation controller 380 that is inelectrical communication with a power transmission cable. For instance,signal flow path 364 may provide monitored input parameters (e.g.,monitored input parameters 51 of FIG. 1-1) from the ECM 5 to the controlmodule 60 for generating the injector command signal 52. In someembodiments, the signal flow path 364 may provide feedback fuel injectorparameters (e.g., feedback signal(s) 42 of FIG. 1-1) to the ECM 5.

The injector driver 50 receives DC electric power from the power source40 of FIG. 1-1 via a power supply flow path 366. The signal flow path364 can be eliminated by use of a small modulation signal added to thepower supply flow path 366. Using the received DC electric power, theinjector driver 50 may generate injector activation signals (e.g.,injector activation signals 75 of FIG. 1-1) based on the injectorcommand signal from the control module 60.

The injector driver 50 is configured to control activation of the fuelinjector 10 by generating suitable injector activation signals 75. Theinjector driver 350 is a bi-directional current driver providingpositive current flow via a first current flow path 352 and negativecurrent flow via a second current flow path 354 to the electrical coil24 in response to respective injector activation signals 75. Thepositive current via the first current flow path 352 is provided toenergize an electrical coil 24 and the negative current via the secondcurrent flow path 354 reverses current flow to draw current from theelectrical coil 24. Current flow paths 352 and 354 form a closed loop;that is, a positive current into 352 results in an equal and opposite(negative) current in flow path 354, and vice versa. Signal flow path371 can provide a voltage of the first current flow path 352 to thecontrol module 60 and signal flow path 373 can provide a voltage of thesecond current flow path 354 to the control module 60. The voltage andcurrent applied to the electrical coil 24 is based on a differencebetween the voltages at the signal flow paths 371 and 373. In oneembodiment, the injector driver 50 utilizes open loop operation tocontrol activation of the fuel injector 10, wherein the injectoractivation signals are characterized by precise predetermined currentwaveforms. In another embodiment, the injector driver 50 utilizes closedloop operation to control activation of the fuel injector 10, whereinthe injector activation signals are based upon fuel injector parametersprovided as feedback to the control module, via the signal flow paths371 and 373. A measured current flow to the coil 24 can be provided tothe control module 60, via signal flow path 356. In the illustratedembodiment, the current flow is measured by a current sensor on thesecond current flow path 354. The fuel injector parameters may includeflux linkage, voltage and current values within the fuel injector 10 orthe fuel injector parameters may include proxies used by the controlmodule 60 to estimate flux linkage, voltage and current within the fuelinjector 10.

In some embodiments, the injector driver 50 is configured for full fourquadrant operation. FIG. 1-3 illustrates an exemplary embodiment of theinjector driver 50 of FIGS. 1-2 utilizing two switch sets 370 and 372 tocontrol the current flow provided between the injector driver 50 and theelectrical coil 24. In the illustrated embodiment, the first switch set370 includes switch devices 370-1 and 370-2 and the second switch set372 includes switch devices 372-1 and 372-2. The switch devices 370-1,370-2, 372-1, 372-2 can be solid state switches and may include Silicon(Si) or wide band gap (WBG) semiconductor switches enabling high speedswitching at high temperatures. The four quadrant operation of theinjector driver 50 controls the direction of current flow into and outof the electrical coil 24 based upon a corresponding switch statedetermined by the control module 60. The control module 60 may determinea positive switch state, a negative switch state and a zero switch stateand command the first and second switch sets 370 and 372 between openand closed positions based on the determined switch state. In thepositive switch state, the switch devices 370-1 and 370-2 of the firstswitch set 370 are commanded to the closed position and the switchdevices 372-1 and 372-2 of the second switch set 372 are commanded tothe open position to control positive current into the first currentflow path 352 and out of the second current flow path 354. These switchdevices may be further modulated using pulse width modulation to controlthe amplitude of the current. In the negative switch state, the switchdevices 370-1 and 370-2 of the first switch set 370 are commanded to theopen position and the switch devices 372-1 and 372-2 of the secondswitch leg 372 are commanded to the closed position to control negativecurrent into the second current flow path 354 and out of the firstcurrent flow path 352. These switch devices may be further modulatedusing pulse width modulation to control the amplitude of the current. Inthe zero switch state, all the switch devices 370-1, 370-2, 372-1, 372-2are commanded to the open position to control no current into or out ofthe electromagnetic assembly. Thus, bi-directional control of currentthrough the coil 24 may be effected.

In some embodiments, the negative current for drawing current from theelectrical coil 24 is applied for a sufficient duration for reducingresidual flux within the fuel injector 10 after a secondary hold currentis released. In other embodiments, the negative current is appliedsubsequent to release of the secondary hold current but additionallyonly after the fuel injector has closed or actuator has returned to itsstatic or rest position. Moreover, additional embodiments can includethe switch sets 370 and 372 to be alternately switched between open andclosed positions to alternate the direction of the current flow to thecoil 24, including pulse width modulation control to effect current flowprofiles. The utilization of two switch sets 370 and 372 allows forprecise control of current flow direction and amplitude applied to thecurrent flow paths 352 and 354 of the electrical coil 24 for multipleconsecutive fuel injection events during an engine event by reducing thepresence of eddy currents and magnetic hysteresis within the electricalcoil 24.

FIG. 2 illustrates a non-limiting exemplary first plot 1000 of measuredcurrent and fuel flow rate and a non-limiting exemplary second plot 1010of measured main excitation coil and search coil voltages for twosuccessive fuel injection events having identical current pulses thatare separated by a dwell time that is not indicative of being closelyspaced, in accordance with the present disclosure. Dashed vertical line1001 extending through each of plots 1000 and 1010 represents a firsttime whereat an end of injection for the first fuel injection eventoccurs and dashed vertical line 1002 represents a second time whereat astart of injection for the second fuel injection event occurs. The dwelltime 1003 represents a period of time between dashed vertical lines 1001and 1002 separating the first and second fuel injection events. In theillustrated embodiment, the dwell time exceeds a dwell time threshold.Thus, the first and second fuel injection events are not indicative ofbeing closely-spaced.

Referring to the first plot 1000, measured current and flow rateprofiles 1011, 1012, respectively, are illustrated for the two fuelinjection events. The vertical y-axis along the left side of plot 1000denotes electrical current in Amperage (A) and the vertical y-axis alongthe right side of plot 1000 denotes fuel flow rate in milligrams (mg)per milliseconds (ms). The measured current profile 1011 issubstantially identical for each of the fuel injection events. Likewise,the measured fuel flow rate profile 1012 is substantially identical foreach of the fuel injection events due to the fuel injection events notindicative of being closely-spaced.

Referring to the second plot 1010, measured main excitation coil andsearch coil voltage profiles 1013, 1014, respectively, are illustratedfor the two fuel injection events. The measured main coil voltage mayrepresent a measured voltage of the electrical coil 24 of FIG. 1-1 andthe measured search coil voltage may represent a measured voltage of asearch coil mutually magnetically coupled to the electrical coil 24 ofFIG. 1-1. The vertical y-axis of plot 1010 denotes voltage (V).Accordingly, when the main excitation coil is energized, magnetic fluxgenerated by the main excitation coil may be linked to the search coildue to the mutual magnetic coupling. The measured search coil voltageprofile 1014 indicates the voltage induced in the search coil which isproportional to the rate of change of the mutual flux-linkage. Themeasured main excitation coil and search coil voltage profiles 1013,1014, respectively, of plot 1010 are substantially identical for each ofthe first and second fuel injection events that are not indicative ofbeing closely-spaced.

FIG. 3 illustrates a non-limiting exemplary first plot 1020 of measuredcurrent and fuel flow rate and a non-limiting exemplary second plot 1030of measured main excitation coil and search coil voltages for twosuccessive fuel injection events having identical current pulses thatare separated by a dwell time that is indicative of being closelyspaced, in accordance with the present disclosure. The horizontal x-axisin each of plots 1020 and 1030 denotes time in seconds (s). Dashedvertical line 1004 extending through each of plots 1020 and 1030represents a first time whereat an end of injection for the first fuelinjection event occurs and dashed vertical line 1005 represents a secondtime whereat a start of injection for the second fuel injection eventoccurs. The dwell time 1006 represents a period of time between dashedvertical lines 1004 and 1005 separating the first and second fuelinjection events. In the illustrated embodiment, the dwell time is lessthan a dwell time threshold. Thus, the first and second fuel injectionevents are indicative of being closely-spaced.

Referring to the first plot 1020, measured current and flow rateprofiles 1021, 1022, respectively, are illustrated for the two fuelinjection events. The vertical y-axis along the left side of plot 1020denotes electrical current in Amperage (A) and the vertical y-axis alongthe right side of plot 1020 denotes fuel flow rate in milligrams (mg)per second (s). The measured current profile 1021 is substantiallyidentical for each of the fuel injection events. However, the measuredflow rate profile 1022 illustrates a variation in the measured fuel flowrate between each of the first and second fuel injection events eventhough the measured current profiles are substantially identical. Thisvariance in the measured fuel flow rate is inherent in closely-spacedfuel injection events and undesirably results in an injected fuel massdelivered at the second fuel injection event that is different than aninjected fuel mass delivered at the first fuel injection event.

Referring to the second plot 1030, measured main excitation coil andsearch coil voltage profiles 1023, 1024, respectively, are illustratedfor the two fuel injection events. The measured main coil voltage mayrepresent a measured voltage of the electrical coil 24 of FIG. 1-1 andthe measured search coil voltage may represent a measured voltage of asearch coil mutually magnetically coupled to the electrical coil 24 ofFIG. 1-1. The vertical y-axis of plot 1030 denotes voltage (V).Accordingly, when the main excitation coil is energized, magnetic fluxgenerated by the main excitation coil may be linked to the search coildue to the mutual magnetic coupling. The measured search coil voltageprofile 1024 indicates the voltage induced in the search coil which isproportional to the rate of change of the mutual flux-linkage. Themeasured main excitation coil and search coil voltage profiles 1023,1024, respectively, of plot 1030 differ during the second injectionevent in comparison to the first fuel injection event. This differenceis indicative of the presence of residual flux or magnetic flux when theinjection events are closely-spaced. Referring to plot 1010 of FIG. 2the measured main excitation coil and search coil voltage profiles 1013,1014, respectively do not differ during the second injection event incomparison to the first fuel injection event when the first and secondfuel injection events are not closely-spaced.

Referring back to FIG. 1-1, exemplary embodiments are further directedtoward providing feedback signal(s) 42 from the fuel injector 10 back tothe control module 60 and/or the injector driver 50. Discussed ingreater detail below, sensor devices may be integrated within the fuelinjector 10 for measuring various fuel injector parameters for obtainingthe flux linkage of the electrical coil 24, voltage of the electricalcoil 24 and current provided to the electrical coil 24. A current sensormay be provided on a current flow path between the activation controller80 and the fuel injector to measure the current provided to theelectrical coil or the current sensor can be integrated within the fuelinjector 10 on the current flow path. The fuel injector parametersprovided via feedback signal(s) 42 may include the flux linkage, voltageand current directly measured by corresponding sensor devices integratedwithin the fuel injector 10. Additionally or alternatively, the fuelinjector parameters may include proxies provided via feedback signal(s)42 to—and used by—the control module 60 to estimate the flux linkage,magnetic flux, the voltage, and the current within the fuel injector 10.Having feedback of the flux linkage of the electrical coil 24, thevoltage of the electrical coil 24 and current provided to the electricalcoil 24, the control module 60 may advantageously modify the activationsignal 75 to the fuel injector 10 for multiple consecutive injectionevents. It will be understood that conventional fuel injectors arecontrolled by open loop operation based solely upon a desired currentwaveform obtained from look-up tables without any information related tothe force producing component of the flux linkage (e.g., magnetic flux)affecting movement of the armature portion 21. As a result, conventionalfeed-forward fuel injectors that only account for current flow forcontrolling the fuel injector, and are prone to instability inconsecutive fuel injection events that are closely-spaced.

It is known when the injector driver 50 only provides currentuni-directionally in a positive first direction to energize theelectrical coil 24, reducing the current to remain stable at zero willresult in the magnetic force of the armature portion and magnetic fluxwithin the fuel injector to gradually decay. However, the response timefor the magnetic force and flux to decay is slow which often results inthe presence of an undesirable level of residual flux when a subsequentconsecutive fuel injection event is initiated. As aforementioned, thepresence of the residual flux may impact the accuracy of the fuel flowrate and injected fuel mass to be delivered in the subsequent fuelinjection event, wherein the presence of the residual flux is at anundesirable level for closely spaced fuel injection events.

FIG. 4 illustrates a series of non-limiting exemplary plots 1300, 1310and 1320, representing measured coil current, magnetic force andmagnetic flux in a magnetic actuator, wherein current provided to thecoil is being controlled in a unidirectional manner, in accordance withthe present disclosure. The measured coil current is indicative ofcurrent provided uni-directionally from an injection driver to anelectrical coil within the magnetic actuator. The horizontal x-axis ineach of plots 1300, 1310 and 1320 denotes time in seconds (s). Plot 1300illustrates the measured coil current having a measured current profile1301. The vertical y-axis along the left side of plot 1300 denoteselectrical current in Amperage (A). Plot 1310 illustrates the measuredmagnetic force having a measured magnetic force profile 1311 responsiveto the measured current profile 1301, with the vertical y-axis along theleft side denoting force in Newton (N). Plot 1320 illustrates themeasured magnetic flux having a measured magnetic flux profile 1321,with the vertical y-axis along the left side denoting flux in weber(Wb). At region 1360 the current is reduced from a positive value tozero. In response thereto, the measured magnetic force profile 1311 isinitially reduced abruptly, whereafter it slowly decays toward somevalue greater than zero while the measured current profile 1301 ismaintained at zero. Similarly, the measured magnetic flux profile 1321decays to a near zero value while the measured current profile 1301 ismaintained at zero. Notably, magnetic flux profile 1321 illustrates aresidual flux level passively attained within the actuator at zero coilcurrent. Passive residual flux will refer to the level of steady-stateresidual flux within the actuator when the coil current is released tozero subsequent to an actuation event.

Bi-directional current can be utilized to improve the response times ofthe magnetic force and flux compared to that of when current is applieduni-directionally, as described above with reference to the non-limitingexemplary plots 1300, 1310 and 1320 of FIG. 4. In addition to currentdriven in the positive first direction to energize an electrical coil,current driven bi-directionally also includes current driven in areversed negative second direction to draw current from the electricalcoil after an end of injection to quickly control the magnetic flux tozero.

FIG. 5 illustrates a non-limiting exemplary plot 1200 of measuredcurrent and flow rate for two successive fuel injection events havingidentical current pulses (e.g., waveforms) that are separated by a dwelltime that is indicative of being closely spaced. Unlike theunidirectional current applied in the positive first direction in plot1020 of FIG. 3, a bi-directional current is utilized to improve theconsistency and stability of the fuel flow rate and resulting injectedfuel mass delivered to the engine. The horizontal x-axis in plot 1200denotes time in seconds (s). The vertical y-axis along the left side ofplot 1200 denotes electrical current in Amperage (A) and the verticaly-axis along the right side of plot 1200 denotes fuel flow rate inmilligrams (mg) per second(s). Dashed vertical line 1201 extendingthrough plot 1200 represents a first time whereat an end of injectionfor the first fuel injection event occurs and dashed vertical line 1202represents a second time whereat a start of injection for the secondfuel injection event occurs. The dwell time 1203 represents a period oftime between dashed vertical lines 1201 and 1202 separating the firstand second fuel injection events. In the illustrated embodiment, thedwell time is less than a dwell time threshold. Thus, the first andsecond fuel injection events are indicative of being closely-spaced

Measured current and flow rate profiles 1211, 1212, respectively, areillustrated for the two fuel injection events. The measured currentprofile 1211 is substantially identical for each of the fuel injectionevents and indicates the current provided to an electrical coil of thefuel injector. Referring to a time immediately after dashed verticalline 1201 whereat the end of injection for the first fuel injectionevent occurs, the measured current profile 1211 indicates that thenegative current in the reversed second direction is being applied todraw current from the electrical coil. As a result of this negativecurrent applied after the end of injection of the first injection eventand prior to the start of injection for the second fuel injection eventat dashed vertical line 1202, residual flux within the fuel injector israpidly reduced to zero such that the fuel flow rate corresponding tothe second fuel injection event is not influenced by the closely spacedfirst injection event. For instance, the measured fuel flow rate profile1212 indicates that the measured fuel flow rate corresponding to thesecond fuel injection event within region 1216 is substantiallyidentical to the measured fuel flow rate corresponding to the first fuelinjection event within region 1215. This is in contrast to the strictlyunidirectional current illustrated in plot 1020 of FIG. 3 that resultsin the second fuel injection event having a measured fuel flow rate thatdeviates from that of the first fuel injection event. As a result,application of the bi-directional current results in the injected fuelmass delivered at the first fuel injection event to be substantially thesame as the injected fuel mass delivered at the second fuel injectionevent even though the fuel injection events are closely-spaced.

FIG. 6 illustrates a non-limiting exemplary plot 1500 for measuredcurrent and measured magnetic flux and a non-limiting exemplary plot1502 for measured search coil voltage during two successive fuelinjection events having identical current pulses separated by a dwelltime. The measured search coil voltage may represent a measured voltageinduced in a search coil that is mutually magnetically coupled to a mainexcitation coil (e.g., electromagnetic coil 24 of FIG. 1-1). Providing asearch coil and measuring voltage of the search coil to obtainflux-linkage is described above with reference to the non-limitingexemplary plots 1010 and 1030 of FIGS. 2 and 3, respectively.

Dashed vertical line 1520 extending through each of plots 1500 and 1502represents a first time whereat an end of injection for the first fuelinjection event occurs and dashed vertical line 1522 represents a secondtime whereat a start of injection for the second fuel injection eventoccurs. The dwell time represents a period of time between dashedvertical lines 1520 and 1522 separating the first and second fuelinjection events. The horizontal x-axis in each of plots 1500 and 1502denotes time in seconds (s).

Referring to the first plot 1500, measured current and magnetic fluxprofiles 1510, 1512, respectively, are illustrated for the two fuelinjection events. The vertical y-axis along the left side of plot 1500denotes electrical current in Amperage (A) and the vertical y-axis alongthe right side of plot 1500 denotes flux in weber (Wb). At the end ofthe first injection event when the measured current profile 1510 isequal to zero at the first dashed vertical line 1520, the direction ofthe current provided to the electromagnetic coil is reversed in anegative direction to values less than zero for a duration until dashedvertical line 1524 whereafter the current abruptly returns to zero.During this duration between dashed vertical lines 1520 and 1524, themeasured magnetic flux profile 1512 is responsively reduced toward zero.However, at dashed vertical line 1524, the measured current profile 1520is increased to a value equal to zero whereat the measured magnetic fluxprofile 1512 responsively stops reducing toward zero and momentarilyincreases and gradually decays toward but does not achieve zero untilincreasing at dashed vertical line 1522 in response to the increasedmeasured current profile 1510 corresponding to the start of injectionfor the second fuel injection event. Thus, the measured magnetic fluxprofile 1512 indicates a presence of residual flux at dashed verticalline 1522 which will influence the magnetic force response time and thedelivered injected fuel mass of the second fuel injection event. As canbe seen from plot 1500, the length of the duration between dashedvertical lines 1520 and 1524 wherein the reversed current is applied inthe negative direction is too short for reducing the measured magneticflux within the fuel injector to zero. This leaves an undesirable levelof residual flux which directly impacts the response time of themagnetic force.

Referring to plot 1502, measured search coil voltage profile 1530responsive to the measured magnetic flux profile 1512 is illustrated. Asthe measured current profile 1510 begins reducing at dashed verticalline 1518 from a positive hold current, a negative rate of changeevidenced by the measured magnetic flux profile 1512 occurs in theflux-linkage between the main excitation coil and the search coil. Thisnegative rate of change in the flux linkage can be correlated to themeasured search coil voltage profile 1530 changing polarity in thenegative direction. When the measured current profile 1510 is increasedtoward zero at dashed vertical line 1524, a positive rate of changeoccurs in the flux linkage and the search coil voltage profile 1530changes polarity in the positive direction. Ideally, the search coilvoltage profile 1530 should go to zero after the polarity change in thepositive direction when the measured current profile is zero 1510.However, because the measured magnetic flux profile 1512 is not zero anddecaying when the reversed current in the negative direction is removedat dashed vertical line 1524, plot 1502 shows that the measured searchcoil voltage profile 1530 is at a value less than zero up until thestart of injection for the second fuel injection event at dashedvertical line 1522. Accordingly, utilizing measurements of the voltageinduced in the search coil, a correlation can be made that removal ofthe reverse current in the negative direction at vertical line 1524 ispremature due to the magnetic flux within the fuel injector not beingentirely removed.

Referring back to plot 1500, dashed line 1540 projecting from themeasured magnetic flux profile 1512 indicates that the magnetic fluxwould be entirely removed if the duration of the measured currentprofile 1510 whereat the reversed current is applied in the negativedirection were extended to dashed vertical line 1526. Accordingly, theperiod of time between dashed vertical lines 1520 and 1526 denotes theoptimal duration for applying the reversed current in the negativedirection to sufficiently remove the magnetic flux within the fuelinjector. In this scenario, the measured search coil voltage 1530 wouldbe zero after changing polarity to positive after dashed vertical line1526.

Assuming a negative current is driven into the coil to reduce theresidual flux to below the passive residual flux level after aninjection event, when the negative current is removed and goes to zero,then any residual flux still within the fuel injector would thereafternaturally decay at a certain time rate of change. It is believed thatthe time rate of change of the residual flux decreases the closer theresidual flux level is to zero. Therefore, since the search coil voltagemagnitude is proportional to the time rate of change of the flux, it isbelieved that the search coil voltage magnitude will be smaller thecloser the residual flux level is to zero since the residual flux closerto zero exhibits smaller time rates of change. Thus, the search coilvoltage may generally be used to indicate the continued presence ofresidual flux in the fuel injector after driving a negative current tothe electromagnetic coil subsequent to an injection event. And, themagnitude of such a search coil voltage may further be indicative of themagnitude of such a remaining residual flux. The search coil voltage mayadvantageously be used in a feedback control module to further refinethe negative current driven through the electromagnetic coil to controlthe residual flux level in the fuel injector. It is recognized thatother measures of residual flux, for example from magneto-resistive orhall effect sensors, may be utilized in similar fashion in a feedbackcontrol module to further refine the negative current driven through theelectromagnetic coil to control the residual flux level in the fuelinjector.

FIG. 7 illustrates one preferred feedback control module employingresidual flux sensing with a search coil. In this example, a deadbeatflux control module uses search coil voltage feedback to establish anoptimum duration at which a negative current is applied to anelectromagnetic coil of a fuel injector to reduce residual flux therein.The deadbeat flux control module 700 can be implemented within theactivation controller 80 of FIG. 1-1. Accordingly, the deadbeat fluxcontrol module 700 will be described with reference to FIG. 1-1. Thedeadbeat flux control module 700 includes a current command generation(CCG) module 702, a deadbeat flux control module 704, a difference unit706, a proportional integral (PI) control module 708, and an injectordriver 710. The control module 60 and the injector driver 50 of theactivation controller 80 of FIG. 1-1 may encompass differentcombinations of those features of the deadbeat flux control module 700listed.

In the illustrated embodiment, a desired fuel flow rate 701 is input tothe CCG module 702. The desired fuel flow rate 701 may be provided froman external module, e.g., the ECM 5, based on the aforementioned inputparameters 51 for achieving a desired injected fuel mass, as describedabove with reference to FIG. 1-1. The CCG module 702 outputs aunidirectional current command 703 indicative of a commanded pull-incurrent and hold-current over a fuel injection event duration toactivate the fuel injector 10 for delivering the desired fuel flow rate701. The term “unidirectional” refers to the commanded pull-in and holdcurrents during the fuel injection event duration being in a positivefirst direction that includes all values for current greater than orequal to zero.

The unidirectional current command 703 is then input to the deadbeatflux control module 704 for commanding a magnitude and optimal durationfor a reversed current in a negative second direction that draws currentfrom the electromagnetic coil 24 after the fuel injection event durationto drive down magnetic flux within the fuel injector 10 to some levelbelow the passive residual flux level. This level to which residual fluxis reduced may be zero or may be some non-zero flux level having amagnitude that is less than the magnitude of the passive residual fluxlevel. Accordingly, the deadbeat flux control module 704 outputs abi-directional current command 705 that includes a first portioncorresponding to the unidirectional current command 703 and a secondportion corresponding to the commanded magnitude and optimal durationfor the reversed current in the negative second direction.

The deadbeat flux control module 704 determines the second portion ofthe bi-directional current based upon measured search coil voltagefeedback 715. As described above with reference to the non-limitingexemplary plots 1500 and 1502 of FIG. 6, voltage induced in a searchcoil mutually magnetically coupled to a main excitation coil (e.g.,electromagnetic coil 24) can be utilized to determine the presence ofresidual flux within the fuel injector after current in the negativesecond direction is removed. In the illustrated embodiment, a voltagesensor integrated within the fuel injector, within control module 60 ofactuation controller 80, or otherwise within another controller measuresthe voltage induced in the search coil and provides the measured searchcoil voltage feedback 715 to the deadbeat flux control module 704. Thus,the measured search coil voltage feedback 715 may be transmitted fromthe fuel injector 10 via feedback signal(s) 42, as described above withreference to the illustrated embodiment of FIG. 1-1. The deadbeat fluxcontrol module 704 can thereby adjust the duration for the reversedcurrent in the negative duration to achieve the optimal duration forentirely removing the presence of residual flux within the fuel injector10. Accordingly, the deadbeat flux control module 704 outputs thebi-directional current command 705 based upon the unidirectional currentcommand 703 and the measured search coil voltage feedback 715.

It will be understood that while the bi-directional current command 705does account for the presence of residual flux via the measured searchcoil feedback 715, the bi-directional current command 705 does notaccount for current present within the fuel injector, e.g., flowingthrough the electromagnetic coil 24. Accordingly, a current feedbackloop includes current feedback 713 of current measured by a currentsensor 712 positioned on a current flow path between the fuel injector10 and the injector driver 710. In some embodiments, the current sensor712 may be integrated within the fuel injector 10. The current feedbackloop further includes difference unit 706 outputting an adjustedbi-directional current command 707 based on a comparison between thebi-directional current command 705 and the current feedback 713 measuredby the current sensor 712.

The adjusted current command 707 is input to a PI control module 708 ofthe current feedback loop whereby a commanded PWM electric power flowsignal 709 is generated and input to the injector driver 710. Based uponthe commanded PWM electric power flow signal 710, which accounts for thecurrent feedback 713 and measured search coil voltage feedback 715within the fuel injector 10, the injector driver 710 maybi-directionally apply current both in the positive first direction 721for energizing the electromagnetic coil 24 for activating the fuelinjector 10 to deliver the desired fuel flow rate 701 and the negativesecond direction 723 for drawing current from the electromagnetic coil24 for the optimal duration after the fuel injection event to remove thepresence of residual flux and improve the response time of the magneticforce.

FIG. 8 illustrates a series of non-limiting exemplary plots 1330, 1340and 1350, representing measured coil current, magnetic force andmagnetic flux in a magnetic actuator wherein flux is controlled usingcurrent applied to the fuel injector in a bi-directional manner. Forinstance, the flux may be controlled using the deadbeat flux controlmodule 700 of FIG. 7 to bi-directionally apply the current to themagnetic actuator. The measured coil current is indicative of currentprovided bi-directionally from a coil driver to an electromagnetic coilof the magnetic actuator. The horizontal x-axis in each of plots 1330,1340 and 1350 denotes time in seconds(s). Plot 1330 illustrates ameasured coil current having a measured current profile 1331. Thevertical y-axis along the left side of plot 1330 denotes electricalcurrent in Amperage (A). Plot 1340 illustrates the measured magneticforce having a measured magnetic force profile 1341 responsive to themeasured current profile 1331, with the vertical y-axis along the leftside denoting force in Newtons (N). Plot 1350 illustrates the measuredmagnetic flux having a measured magnetic flux profile 1351 responsive tothe measured current profile 1331, with the vertical y-axis along theleft side denoting flux in weber (Wb). At region 1361 the measuredcurrent in a positive direction is reduced from a positive value untilzero and then the current is driven in a reversed negative direction toa value less than zero for an optimum duration. In response to thecurrent driven in the reversed negative direction, the measured magneticforce profile 1341 is abruptly reduced to a desired value and themeasured magnetic flux profile 1351 is abruptly reduced to zero.Accordingly, when the current is applied to the electromagnetic coil inthe reversed negative direction, current is being drawn from theelectromagnetic coil to directly control the magnetic flux to a levelbelow the passive residual flux level, preferable to zero, and themagnetic force to reach consummately lower values in response times muchquicker than those illustrated in the non-limiting exemplary plots 1300,1310 and 1320 of FIG. 4 when the current is merely reduced to andmaintained at zero and not driven in the negative second direction.

The disclosure has described certain preferred embodiments andmodifications thereto. Further modifications and alterations may occurto others upon reading and understanding the specification. Therefore,it is intended that the disclosure not be limited to the particularembodiment(s) disclosed as the best mode contemplated for carrying outthis disclosure, but that the disclosure will include all embodimentsfalling within the scope of the appended claims.

1. An electromagnetic actuation system, comprising: an actuatorcomprising an electrical coil, a magnetic core, and an armature; acontrollable bi-directional drive circuit for selectively drivingcurrent through the electrical coil in either of two directions; and acontrol module providing an actuator command to the drive circuiteffective to drive current through the electrical coil in a firstdirection to actuate the armature and in a second direction subsequentto armature actuation to oppose residual flux within the actuator, saidcontrol module comprising a residual flux feedback control moduleconfigured to adapt said actuator command to converge residual fluxwithin the actuator to a preferred flux level.
 2. The electromagneticactuation system of claim 1, wherein said preferred flux level comprisesa zero flux level.
 3. The electromagnetic actuation system of claim 1,wherein said preferred flux level comprises a non-zero flux level havinga magnitude that is less than the magnitude of a level of residual fluxpassively attained within the electrical coil at zero current.
 4. Theelectromagnetic actuation system of claim 1, wherein said residual fluxfeedback control module comprises an electrical coil current feedbackloop configured to adapt said actuator command to converge electricalcoil current to a desired electrical coil current.
 5. Theelectromagnetic actuation system of claim 4, wherein said residual fluxfeedback control module comprises a search coil mutually magneticallycoupled to the electrical coil configured to sense time rate of changeof the residual flux within the actuator.
 6. The electromagneticactuation system of claim 1, wherein said residual flux feedback controlmodule comprises a search coil mutually magnetically coupled to theelectrical coil configured to sense time rate of change of the residualflux within the actuator.
 7. The electromagnetic actuation system ofclaim 1, wherein said residual flux feedback control module comprises amagnetoresistive sensor configured to sense the residual flux within theactuator.
 8. The electromagnetic actuation system of claim 1, whereinsaid residual flux feedback control module comprises a hall effectsensor configured to sense the residual flux within the actuator.
 9. Theelectromagnetic actuation system of claim 1, wherein said residual fluxfeedback control module comprises a deadbeat control module.
 10. Amethod for controlling an electromagnetic actuator, comprising: drivingcurrent though an electrical coil of the actuator in a first directionwhen an actuation is desired; and, when the actuation is not desireddriving current through the electrical coil in a second directionsufficient to reduce residual flux within the actuator below a levelpassively attained within the actuator at zero coil current, whereindriving current through the electrical coil in the second directioncomprises adapting the current through the electrical coil in the seconddirection based upon a residual flux feedback to converge residual fluxwithin the actuator to a preferred flux level.
 11. The method forcontrolling the electromagnetic actuator of claim 10, furthercomprising: adapting the current through the electrical coil in thesecond direction based upon an electrical coil current feedback toconverge electrical coil current to a desired electrical coil current.12. The method for controlling the electromagnetic actuator of claim 10,wherein said residual flux feedback comprises a voltage induced within asearch coil mutually magnetically coupled to the electrical coil. 13.The method for controlling the electromagnetic actuator of claim 10,wherein adapting the current through the electrical coil in the seconddirection based upon a residual flux feedback comprises inputting saidresidual flux feedback into a deadbeat control module.
 14. A system forcontrolling actuation of a fuel injector, comprising: a fuel injectorcomprising an electrical coil, a magnetic core, and an armature; acontrollable bi-directional drive circuit responsive to a currentcommand for driving current through the electrical coil in a firstdirection to actuate the armature, in a second direction subsequent toarmature actuation for a predetermined duration, and thereafter to zero;and a control module configured to determine a residual flux in the fuelinjector after the current through the electrical coil is driven to zeroand adapt the current command to control the predetermined durationbased on the residual flux.
 15. The system for controlling actuation ofthe fuel injector of claim 14, wherein said control module is furtherconfigured to determine the current through the electrical coil andadapt the current command based on the current through the electricalcoil.
 16. The system for controlling actuation of the fuel injector ofclaim 14, further comprising a search coil mutually magnetically coupledto the electrical coil, said control module further configured todetermine a time rate of change of the residual flux within the fuelinjector based on the search coil, wherein the residual flux in the fuelinjector after the current through the electrical coil is driven to zerois determined based on the time rate of change of the residual fluxwithin the fuel injector.
 17. The system for controlling actuation ofthe fuel injector of claim 14, further comprising a magnetoresistivesensor disposed within a flux path within the fuel injector, saidcontrol module further configured to determine the residual flux withinthe fuel injector based on the magnetoresistive sensor.
 18. The systemfor controlling actuation of the fuel injector of claim 14, furthercomprising a hall effect sensor disposed within a flux path within thefuel injector, said control module further configured to determine theresidual flux within the fuel injector based on the hall effect sensor.19. The system for controlling actuation of the fuel injector of claim14, wherein said control module comprises a deadbeat control module. 20.The system for controlling actuation of the fuel injector of claim 16,wherein said control module comprises a deadbeat control module.